Hoist having load regulation



1 United States Patent Inventor Howard C. Stevens, Jr.

Muskegon, Michigan Appl. No. 776,193

Filed Nov. 15, 1968 Patented Nov. 24, 1970 Assignee Dresser IndustriesInc.

Dallas, Texas a corporation of Delaware HOIST HAVING LOAD REGULATION 10Claims, 5 Drawing Figs.

US. Cl 254/ 169 Int. Cl B66d 1/00 Field of Search 254/167- I7 I:74/(Consulted): l88/(Consulted) [56] References Cited UNITED STATESPATENTS 1,684,185 9/1928 Kitterdge 254/171 2,393,120 1/1946 Perman254/170 Primary ExaminerHarvey C. Hornsby Attorneys-Robert W. Mayer,Daniel Rubin, Peter J. Murphy,

Frank S. Troidl, Roy L. Van Winkle and William E. Johnson, Jr.

ABSTRACT: A hoist having a regulator to limit load raising capacity to apredetermined maximum. The regulator is operably mounted between thehoist input by which a load is raised or lowered and the hoist output onwhich a load is to be contained. in the event of an applied load inexcess of the predetermined limit set by the regulator, the hoist isrendered inoperable for raising the load but continues operable to lowerthe load. With the existence of the latter condition, an attempt toraise the load produces an audio and sensual signal transmitted to theoperator instantly alerting him to the condition.

Patented Nov. 24,1970 3,542,341

Sheet I l of 4 ATTORNEY HOWARD C. STEVENS, JR.

, Patented-Nov'.' 24,1970 I 3,542,341

Shoot 2 0t 4 INVENTOR HOWARD c. STEVENS, JR.

ATTORNEY Patented Nov 24, 1970 Sheet INVENTOR HOWARD C. STEVENS, JR.

ATTOR NEY Patented Nov. 24, 1970 Shoot 1; of 4 m Ofm INVENTOR HOWARD C.STEVENS JR.

ATTOR NEY l I'IOIST HAVING LOAD REGULATION BACKGROUND OF THEINVENTION 1. The field of art to which the invention pertains generallyincludes the art of article handlingas specifically directed to hoistingequipment having a torque-limiting clutch mechanism for overloadprevention.

2. Hoists, and in particular hand operated chain hoists, for elevatingarticles or other similar type loads are extensively employed in manyapplications of industrial life. Noteworthy users are the chemicalcompanies, the'automotive companies, shipyards and others havingoperations requiring frequent hoisting of parts, cargo or the like. Eachhoist when sold is built to a manufacturer's specification fora ratedload capacity within which the hoist is capable of being safely used.When the rated capacity is observed and the hoists are otherwisemaintained they can be expected to provide many years of trouble freelife. However, despite the usual conspicuous display of rated capacityit is common practice among hoist operators to generally ignore therating and determine hoist input capacity solely by the hoist ability tooperate with a particular load. Because it isfrequently difficult toprejudge an actual load to be encountered, safe operating capacity isjudged by the operator purely on the basis of whether the hoist cantolerate the load without failure.ln the case of handoperated hoists,the input power is limited only by the operatoris physical strengthwhich via the mechanical leverage provided by the hoist permitsmisjudgment substantially greater than intended by themanufacturer.While most marketed hoists have built-in safety factors permittingoccasional and moderate exceeding of rated capacities without equipmentdamage, it is both economically impractical and impossible for themanufacturer to design a hoist in anticipation 'of every field conditionto which the hoist will likely be subjected.

Hoist failure can of course result in load dropping and consequentdamage not least of which is personal injury or loss of life. Hoistfailure from the inability to elevate a load from the ground producesthe minimal injury in that the failure is immediately apparent to theoperator and no dropping of load occurs. What frequently happens howeveris a form of progressive failure from frequent overloading permitting anactual failure from a load even within the rated hoist capacity. It canbe well appreciated that this latter situation presents a real legaldilemma for the hoist manufacturer in the determination of productliability.

Therefore despite long recognition of the overload problem, hoistmanufacturers have not heretofore been practically able to protect theirequipment and consequently themselves from the after sale abuseinflicted by their customers. Various techniques toward resolving thisdifficulty have been tried including the obvious of providing a weighscale on the load or output side of the hoist perrnitting preloaddetermination by the operator. It has been found however that suchscales are either ignored or not serviceably maintained, so thatoverloading continues unchecked and notwithstanding. Moreover,

while overload slip clutches of various types are well known for maymany other industrial applications, it has not been known heretofore howto utilize such a clutch with a hoist for positive control which withinreasonable limits also prevents dropping yet enables lowering ofasuspended overload.

SUMMARY prevented. Consequently, a greater degree of legal protectionafter sale of the equipment is afforded a manufacturer by preventingthis form of equipment abuse under field conditions otherwise beyond themanufacturers control. Not only does a hoist in accordance withinvention hereofminimize the LII possibilityof overload withinprescribed limits, but moderate overload condition incurred during loadsuspension will not result in a load fall with consequent damage orpersonal injury. In addition when overload is incurred, the regulatordevice hereof emits an audio and sensual signal to the operator clearlyindicating thata state of overload is being experienced, Moreover,despite moderate overload condition, the hoist hereof continues operablefor lowering the load to ground or other safe level whereat the excessload can be removed.

It is therefore an object of the invention to provide a novel loadlifting hoist inherently capable ofoperably controlling appliedoverload.

It is a further object ofthe invention to provide a novel load inglifting hoist having it contained load regulator for prevent ing inputoverload abuse thereof.

It is a further object ofthe invention to provide a hoist in ac cordancewith the aforesaid objects capable of emitting a signal indicating theexistence of an input overload condition.

It is still further object of the invention to provide a hoist inaccordance with the aforesaid objects adapted for hand chain operationand in which an audio and sensual signal is emitted to the operator atthe time an input overload is incurred.

' BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevation view partlyin section of a first hoist embodiment constructed in accordanceherewith;

FIG. 2 is sectional elevation taken substantially along the lines 22ofFIG. 1;

FIG. 3 is an elevation view partly in a section of a second hoistembodiment constructed in accordance herewith;

FIG. 4 is an elevation view taken substantially along the lines 4-4 ofFIG. 3; and

FIG. 5 is an isometric exploded view of the regulator device of FIGS. 1and 2 to facilitate a better understanding thereof.

Referring now to the drawings and in particular to FIGS. 1, 2, and 5there is illustrated a hand chain hoist which may be an adaptation ofatype disclosed in US. Pat. No. 2,739,789 commercially suitable for 2 to10 load on rated load capacity. The hoist includes a generally enclosedhousing 10 having an upwardly extending hook I l for attaching thedevice to a beam or other suitable stationary overhead support.Extending outward beneath the frame from a chain block wrap therein isan extended length of output load suspension chain l2 containing producehook 13 on which to receive a load to be lifted in a conventionalmanner. Leftward of chain 12 as viewed in FIG. 1, is an endless inputdrive chain 16 which depends downward to within ready grasp of anoperator for operating the hoist whereby hook 13 is caused to raise orlower as a function of the direction in which chain 16 is caused tomove.

Supported within the housing is a chain wheel 17 receiving chain 16 tobe rotated thereby and on which is mounted for coaxial rotationtherewith a load regulating device hereof generally designated 20 as'will be described. The regulator device is in turn coaxially mounted ona braking mechanism 21 of the conventional Weston type as for exampledisclosed in the aforementioned US. Pat. No. 2,739,789 Coaxially coupledto the brake via splines 24 is the central operating shaft 22 by whichoperator imposed force applied to chain 16 is translated into verticalmovement of chain 12 and hook 13. Consequently, a pull applied by theoperator to chain 16 in the appropriate direction for raising hook I3 istransmitted to handwheel 17 and regulator 20 wherefrom it is conductedthrough brake 2] IQS/ldf! 22 on which is operobly secured chain 12 forresponsive vertical movement thereto. Hence, when rain ing a loadsupported on hook 13 within the normal rated capacity of the equipmentthe operator's input raising force applied via chain 16 will betransmitted through the regulator 20 in a direct coupled relation aswill be explained. However, where the load on hook 13 either initiallyor subsequently exceeds the preset control limit of the regulator,further imposed operator lifting force on hand chain 16 will not producefurther elevating of the hook 13. Instead at such time as the lattercondition arises,

further pull on the hand chain for elevating the load will produce loudaudible clicking with a predetermined drag torque on the chain both ofwhich signal the operator that an overload condition has been reached.

The load regulator hereof as seen in the FIGS. 1, 2 and 5 comprises aplurality of axially contiguous components including a preassembledtandem or laminated construction maintained assembled via angularlydisplaced rivets 27. Aperture 33 within the radial wheel flange 40.concentrically receives the end portion of the assembly which is securedto outer brake hub 28 on the control side of the brake by means of aplurality of angularly displaced bolts 29. Comprising the latterassembly is'a holddown plate 32 mounted facing against the brake hub butrotatably free of the chain wheel, a series of retaining plates 34, 3S,and 36, a spacer 37 and a second holddown plate 38 of generally largerdiameter than the other preassembled components thereof. Secured bymeans of angularly displaced rivets 41 to the chain wheel rotatably freeof the brake and radially outward of the retaining plates is an annulardetent plate 42. Disposed in a compressed drag relation affording, forreasons as will be explained, a predetermined torque friction betweenthe opposing faces of the detent plate and the radially outwardmostportion of holddown plate 38 is a wave washer 45 ofa type commerciallymarketed.

To operate the hoist within rated capacity the relatively movableregulator assembly secured to brake hub 28 is directly coupled 'with thedetent plate 42 secured to chain wheel 17, This is achieved by means ofretainer rings 34, 35, and 36 having a plurality of coextensive radialslots 47 communicating in radial alinement with corresponding notches 48in the detent plate. The axial alinement of the latter elementsmaintained by means of adjacent holddown plate 32 and spacer 37respectively. Supported within each of the slots is a compressed coilspring 49 constantly urging an axially parallel roller 50 into thecorresponding notch of the detent plate. As can be seen in FIG. 2, therollers 50 are of a diameter less than the width of slot 47 permittingfree radial movement of the .roller therein in opposition to the springbias while notch 48 is of a depthand configuration permitting onlypartial roller penetration insufficient to separate the rollers from theretainer plates. In this relation the roller diameter is effectivelyoverlapped radially by the relatively movable edges of the retaining anddetent plates essentially providing an interlock therebetween. By thismeans, the coupled relation between these latter components for drivingshaft 22 is maintained from chain wheel 17 as a limiting function of theimposed load on hook 13.

Where the applied hook load either initially is in excess of theregulator setting or is increased under load beyond the regulatorsetting, a further attempt to operate the hoist in an upward directionovercomes the coupling bias imposed by springs 50 and forces or ejectsthe rollers radially inward of the retainer ringsuntil clear of thedetent plate. When this latter condition occurs a relative slippingaction develops between the uncoupled components representing operationduring an overload condition at which time further operation of thehoist to raise the load is positively prevented. While such overload isbeing experienced by the operator, a loud audible ratchetlike clickingnoise is generated between the relative moving notches 48 and the biasedrollers 50 signalling existence of the condition. At thesame time, therelative movement encounters the torque resistance imposed by wavewasher 45 and which is fed back via the input hand chain to be felt bythe operator in form of a hand pull. The washer imposed resistanceprevents releasing the chain to a zero torque which could be potentiallydangerous to the operator caught off-balance in exerting a raising forceon the chain. By maintaining a minimum wave washer torque approximately20 percent of the torque required to lift rated load, the operator isgiven an opportunity to regain his stance without losing balance andfalling when the overload condition has suddenly and unexpectedly beenreached.

The precise load condition at which the regulator will respond withoverload operation can be accurately preset. By an appropriatecombination of selecting the machined angle of notch 48 against whichroller 50 will be ejected in attempting to raise the hoist against anoverload, the number of rollers 50, and the spring rate of springs 49,the hook loading condition for overload can be preset or varied. Whileany desired load condition relative to rated hoist capacity can bepreset as desired, it is usual to set this operating point atapproximately percent of rated capacity. With a symmetricalconfiguration of notches 48, there is provided a similar rolling actionin either direction for raising or lowering. Since approximately 20 to25 percent as much torque is normally required to lower as compared toraising a particular load, the notch angles can be relatively changed toprovide any desired operating characteristics. That is, by increasingthe contained approach angle in notch 48 relative to a line of tangencyon the retaining plate peripheries, it is possible to alter theoperating characteristics to reduce the overload limit or otherwise besuitably adapted to various conditions of use.

Should an overload condition reasonably within the physical capacity ofthe components be first incurred during suspension of a load, as byadding load in flight or while elevated, the hook position is instantlymaintained against falling independent of the regulator. At that instantbrake 21 is operable by means of load side radial brake flange 25 andcontrol side brake flange 28 engaging against friction shoe 52.Therefore, while further lifting of the load is prevented by regulator20, lowering the entire load to the ground or other supporting positioncontinues possible via the hand chain in the normal operating mode. Itshould be recognized of course that the regulator is ineffective toprevent overloading on descent except to the extent the operator waspreviously alerted on ascent. Where, for example, the hoist isprincipally employedfor lowering loads, overloading abuse of theequipment cannot be minimized by means of the regulator.

Referring now to FIGS. 3 and 4 there is illustrated a modification ofthe above as herein intended for lower rated capacity loads on the orderof approximately 4 to V2 ton of lift and similar components as beforehave been given the identical character reference numbers for clarity ofunderstanding herein. Specifically, the upper brake hub section 28includes axial shoulders 54 and 55 on which is respectively supported aback plate 56, a washer spacer 57, and a holddown plate 58 all securedtogether in laminated tandem relation via rivets S9. Secured compressedbetween the radially outward portion of the holddown plate and theinside face (it) of the chain wheel is wave washer 45 providing a biastorque resistance as before. In order to maintain a coupling relationbetween the laminated section and the chain wheel the outer diameter ofhub 28 includes coextensive slots 47 each of which contain a spring 49biasing a roller 50 outwardly into a notch 62 formed in the internaldiameter of the chain wheel.

In operation, the unit of FIGS. 3 and 4 is substantially similar asdescribed previously in connection with embodiment of FIGS. 1-, 2, and 5being modified to accommodate relatively smaller operating parts for areduced load capacity equipment. When the operator attempts to raise anoverload,

the rollers 50 are forced radially inward of slots 47 to becomedisengaged from the hand wheel notches 62. This as before produces aloud audible signal with a similar wave washer torque imposed to preventthe operator from losing his balance as the overload condition issuddenly encountered.

By the above description there is disclosed a novel hoist constructioncontaining an integral load regulator by which input overloading of thehoist beyond permissible limits is positively prevented. When suchoverload condition is reached both an audible and felt sensation istransmitted to the operator as a signal of existence of the overloadthereby to instantly alert him of the condition. At the same time, evenduring existence of the condition, the unit hereof continues operablefor the purpose of lowering a suspended load while securing the loadagainst falling is maintained independent of the regulator device-Thehoist hereof is highly effective in achieving a greater degree ofprotection long sought by manufacturers of hoisting equipment yetretaining the desirably braking feature commonly contained in hoistspreviously available commercially. Thus by the simple relativelyuncostly addition to theequipment of a regulator essentially in the formof a roller detent type clutch, applicant has solved a long standingneed which has plagued the industry for many years.

Since many changes could be made in the above construction and manyapparently widely different embodiments of this invention vcould be madewithout departing from the scope thereof, it is intended that all mattercontained in the drawings and specifications shall be interpreted asillustrative and not in a limiting sense.

lclaim: I

l. A hoist for the raising and lowering of loads comprising incombination:

a. an output suspension on which to receive a load;

b. input drive means responsive to a correlated directional inputthereto for operably controlling the raising and lowering of said outputsuspension; and

c. load regulator means operably interposed between said outputsuspension and said input drive means to limit the maximum load raisingcapacity, said regulator means comprising:

1. a first section connected to said input drive means for movementtherewith; 2. a second section connected to said output suspension formovement therewith; and 3. detent coupling means operable to maintainsaid first and second sections connected for conjoint movement when aninput is imposed on said drive means to raise a load on said outputsuspension less than a predetermined maximum and is operable todisconnect said first and second sections from said last-recitedrelation when the imposed drive input is to raise a load on said outputsuspension greater than said predetermined maximum. 7 2. A hoistaccording to claim 1 including signal generating means operativeinresponse to a raise input to said drive means for transmitting adiscernible signal to an operator indicating a disconnectcondition ofsaid coupling means.

' 3. A hoist according-to claim I in which said sections are coaxiallymounted for rotation, and said detent coupling means comprises radiallyextending angularly displaced slots in one of said sections, notches inthe other of said sections 4. A hoist according to claim 3 in which saidslot member comprises a roller and said biasing means comprises aspring. and said rollers are forced from said notches in opposition tothe spring to disconnect said first and second sections in response toan overload imposed on said input drive means permitting relativemovement between said sections.

5. A hoist according to claim 4 in which relative movement between saidsections produces a discrete audible signal indicative of an overloadcondition.

6. A hoist according to claim 5 in which relative movement between saidsections also encounters a torque resistence of predetermined proportionrelative to said maximum load at which disconnect occurs between saidsections.

7. A hoist according to claim 1 including means maintaining a minimumpredetermined torque resistance on said input means when said firstsection becomes disconnected from said second section. 4 8. A hoistaccording to claim 7 in which said input means is chain operated fromhuman input and said minimum torque maintained during the disconnect ofsaid first and second sections provides a sensual signal to the operatorindicative of an existin overload condition. I

9. A 01st according to claim 8 in which said predetermined torqueresistance is provided by resistance means interposed between therelatively movable disconnected regulator sections.

10. A hoist according to claim 8 including brake means operative tomaintain a. suspended load against falling, said brake means having twointerengaging sections operatively interposed between said secondregulator section and said output suspension.

